Filter device

ABSTRACT

A filter device having a filter housing (1) with a fluid inlet (13) for raw fluid and with a fluid outlet (3) for filtrate and with at least one one-piece or multi-piece filter insert (5, 7) which is received in the filter housing (1) and can be cleaned using at least one backflushing member (21) in counter-current to the filtration direction, which member can, by means of a fluid-guiding driveshaft (23) of a rotary drive (35), be moved along the inner side (19) of the respective filter insert (5, 7) and has, at its end adjacent to this inner side (19), a gap-shaped passage opening (39) that runs parallel to the axis of rotation of the driveshaft (23) and discharges into a flow space (41; 57; 67) fluidically connected to the driveshaft (23), which space at least partially continuously nar¬rows in the direction of the driveshaft (23) in a first plane in which the passage opening (39) lies, is characterized in that, in another second plane transverse to the first plane, the flow space (41; 57; 67) at least partially continuously widens proceeding from the passage opening (39) in the direction of the driveshaft (23).

The invention concerns a filter device comprising a filter housing with a fluid inlet for unfiltrate and a fluid outlet for filtrate and with at least one single-part or multi-part filter insert accommodated inside the filter housing, wherein said filter insert may be cleaned through a reverse flow with at least one backflush device, which is moveable by means of a fluid-conducting drive shaft of a rotary drive on the inside of the respective filter insert, and is provided with a slot-shaped flow passage at its end that is adjacent to said inside, wherein said slot-shaped flow passage extends parallel to the rotational axis of the drive shaft and which leads into a flow chamber that has a fluid connection with the drive shaft, wherein said flow chamber tapers at least partially in the direction of the drive shaft in a first plane in which the flow passage is located.

The operational reliability and life span of combustion engines is largely dependent on the high quality of the lubricating oil. In particular the continuous operation of diesel engines, which in maritime applications, for example, are operated with heavy fuel oil, makes high demands on the quality of lubricating oil, so that in applications such as these the use of filter devices to clean the lubricating oil is essential. In this respect it is prior art to use filter devices in which the filter inserts can be backflushed to achieve longer operating periods between filter insert changes and thus reduce the maintenance costs. An example for the prior art, described in document DE 34 43 752 A1, is a filter device of the kind described above.

The cleaning efficiency in devices of this kind depends largely on the path taken by the backflush stream which, at the pressure difference that is available at the slot-shaped flow passage, passes through the flow chamber to the fluid-carrying, i.e. hollow, drive shaft. The pressure difference present during the backflush operation at the slot of the flow passage, which is for example 1.5 bar with a system-generated backflush pressure and a drive shaft at ambient pressure, is designed to achieve a maximum entry velocity at the slot and a maximum backflush volume flow. To come closer to this goal, the described, known filter device provides for a reduction of the flushing cross-section, which is effective during the flushing process, in such a way that the backflush process is only applied to one of two backflush devices. To this end the known filter device is provided with a control facility, which controls the alternating operation of the backflush devices by splitting the sludge discharge over two flushing connections, each of which has a fluid connection with a backflush device. Such a splitting of the sludge discharge, which requires a valve device at each flushing connection, nullifies at least partly the advantages of the effective cleaning action. Moreover, this design runs the risk of blocking the sludge discharge through deposits, in particular in the valve devices at the flushing connections.

Based upon said prior art it is the object of the invention to provide a filter device of the kind described at the outset, which is characterized by a particularly effective cleaning action whilst employing a simple design.

This object is met according to the invention by a filter device that bears the characteristics of claim 1 in its entirety.

According to the characterizing part of claim 1 a significant feature of the invention lies in the fact that in a further second plane, which extends transverse to the first plane in which the flow passage is located, the flow chamber widens out, continually at least in part, starting from the flow passage and in the direction of the drive shaft. Due to said expansion the flow chamber forms a kind of diffuser. This leads to a reduction in pressure loss and thus to the maximization of the backflush volume flow as well as the entry velocity at the slot of the flow passage. Due to the immediate proximity of the slot to the filter material, the cleaning action is particularly effective. The elimination of the valve devices, as provided by the described, known solution, ensures a particularly reliable operating behavior whilst simple in design.

Advantageously, the flow chamber in the first plane may be continuously tapered as a kind of inlet funnel.

In particularly advantageous exemplary embodiments the arrangement may be such that, starting from the slot-shaped flow passage, formed in the first plane are at least

-   -   one boundary wall of the inlet funnel extending obliquely and a         further boundary wall extending level;     -   two boundary walls extending obliquely and in a straight line;     -   two boundary walls extending parabolically; and     -   one boundary wall obliquely and in a straight line, and the         further boundary wall curved.

In exemplary embodiments in which, in the direction of the flow linkage of the flow chamber to an internal fluid passage of the drive shaft, the respective flow chamber merges with its boundary walls into a tube-shaped or channel-shaped section in which the boundary walls extend in a straight line, a particularly homogenous velocity profile of the backflush volume flow results.

Concerning the expansion of the flow chamber in the direction that extends transverse to the plane of the slot of the flow passage, the arrangement may advantageously be such that, in this second plane, the flow chamber expands from the slot-shaped flow passage in the direction of the internal fluid passage of the drive shaft in a conical manner with straight boundary walls.

In advantageous exemplary embodiments the flow chamber, at its exit from the backflush device in the direction of the respective filter insert, is provided with at least one fillet at the boundary walls of the slot-shaped flow passage, which extends parallel to the rotational axis of the drive shaft. The fillet forms a type of control surface along which deposited particles that accumulate during the rotational movement on the backflush device are guided along the fillet to the entry area of the flushing slot where, due to the high entry velocity, the maximum detaching force is present.

At an area ratio between slot inlet and channel exit, which is in the range from 0.2 to 2.0, preferably between 0.3 to 1.0, a homogenous velocity profile of the backflush volume flow results that facilitates the sludge outflow.

The expansion of the slot-shaped flow passage of height to its width is preferably in the range from 10 to 100, preferably in the range from 30 to 70.

Of particular advantage is where the ratio of the width of the slot-shaped flow passage to the free diameter of the tube-shaped or channel-shaped section, which forms the transition to the internal fluid passage of the drive shaft, is between 0.05 and 0.5.

In particularly advantageous exemplary embodiments wing-like flow guide vanes are disposed inside the flow chamber, which extend at least in part from the slot-shaped flow passage away in the direction of the channel exit.

Preferably at least parts of the flow guide vanes extend in a curved or straight manner, and extend fully between the boundary walls of the backflush device, which extend parallel to the rotational axis of the drive shaft.

A particularly advantageous flow pattern may be achieved if at least one flow guide vane protrudes, starting from the slot-shaped flow passage, further into the flow chamber than at least one further flow guide vane, wherein the further protruding flow guide vane, which is preferably disposed in the center of the slot-shaped opening of the flow passage, extends from the same in the direction of the inside of the flow chamber. In this instance the fluid advantageously passes inside the flow chamber from the slot inlet without diversion of the overall flow of the backflush volume up to before the channel exit.

Preferably, the respective backflush device, which faces the internal wall of the respective filter insert with its one free end face, is moved past said internal wall without a gap by means of the rotatable drive shaft.

In particularly advantageous exemplary embodiments, inserted backflush devices are exchangeably retained in an associated retainer housing, which is disposed on the drive shaft. Using the same design of drive shaft and associated rotational drive, the device may be adapted to the respective operating conditions in that in retainer housings on the drive shaft, the number of which depends on the number of filter inserts, a desired number of backflush devices are inserted, the quantity of which as well as the flow chamber geometry may be chosen without restriction.

The arrangement may therefore be such that multiple backflush devices are inserted along the drive shaft, one above the other, wherein they are disposed

-   -   in at least two groups combined at different circumferential         positions on the drive shaft, preferably diametrically opposed         to each other with respect to the rotational axis of said drive         shaft,     -   in one group, exclusively on one side of the drive shaft, or     -   in alternating succession on opposite sides of the drive shaft.

The invention will now be explained in greater detail by way of the exemplary embodiments depicted in the drawing. Shown are in:

FIG. 1 a schematically simplified longitudinal cross-section of an exemplary embodiment of the filter device according to the invention;

FIG. 2 a vertical cross-section of the flow chamber of an individual backflush device of the exemplary embodiment in FIG. 1;

FIG. 3 a horizontal cross-section of the flow chamber of the backflush device in FIG. 2;

FIG. 4 a much enlarged representation of the area designated with IV shown in FIG. 3;

FIG. 5 a schematically simplified vertical cross-section of a second exemplary embodiment of the filter device according to the invention;

FIG. 6 a vertical cross-section of the flow chamber of an individual backflush device of the exemplary embodiment in FIG. 5;

FIG. 7 a horizontal cross-section of the flow chamber in FIG. 6;

FIG. 8 a perspective view, drawn smaller compared to a practical embodiment, of an individual backflush device of the exemplary embodiment in FIG. 5;

FIG. 9 a vertical cross-section of the backflush device in FIG. 8, shown in approximately natural size;

FIGS. 10 & 11 a front view and rear view respectively of the backflush device of FIGS. 8 and 9;

FIG. 12 a horizontal cross-section of this backflush device;

FIGS. 13 & 14 a vertical and horizontal cross-section respectively of the flow chamber of an individual backflush device according to a third exemplary embodiment;

FIG. 15 a schematically simplified vertical cross-section of a fourth exemplary embodiment of the filter device according to the invention;

FIG. 16 a vertical cross-section of the backflush device used for a filter insert in the exemplary embodiment of FIG. 15;

FIG. 17 a modified version compared to the exemplary embodiment of FIGS. 15 and 16 in vertical cross-section, showing the backflush devices formed by inserts, and inserted into a retainer housing;

FIG. 18 a perspective view of a retainer housing for four backflush devices, formed by an insert each, depicting an insert prior to insertion;

FIGS. 19a-19c graphical representations of examples for possible height distributions of inserted backflush devices; and

FIGS. 20a-20c diagrammatic representations of three possible distributions of backflush devices over the circumference of respective filter inserts.

In FIG. 1, which depicts an exemplary embodiment of the filter device according to the invention, a filter housing as a whole is designated with the number 1. Disposed on the side of the circular, cylinder-shaped filter housing 1 is a fluid outlet 3 for filtrate. Disposed inside the filter housing 1, one above the other, is an upper filter insert 5 and a lower filter insert 7, through which the flow passes from inside to outside during the filtration process, wherein the unfiltrate may be supplied to both filter inserts 5 and 7 from a lower inlet side 9. A pre-filter is disposed as inlet filter 11 upstream of the inlet side 9, through which unfiltrate may be supplied from an unfiltrate inlet 13. When used in maritime applications the inlet filter 11 is provided as a so-called fish strainer.

For the purpose of cleaning deposits off the filter material 19 from the upper filter insert 5 and the lower filter insert 7 during backflushing actions, a backflush arm 15 is provided for the upper filter insert 5 and a backflush arm 17 is provided for the lower filter insert 7, each of which is provided with three backflush devices 21. In the exemplary embodiment shown, the backflush arms 15 and 17 are disposed, offset from each other by an axial distance and 180° radially to each other, on a drive shaft 23, the upper end of which is pivotally supported by a bearing 25 at the upper housing cover 27 of housing 1 as well as by a lower bearing 29. The open end of the drive shaft 23, which is formed by a tube, is at this point connected to a sludge discharge tube 31, attached to which is a motor-actuated backflush valve 33, which closes the discharge tube 31 during filter operation and opens it for a backflush operation. To provide a rotational drive, the hollow drive shaft 23 is coupled at the upper bearing 25 to the gearbox 35 of an electric gear motor (not shown).

During filter operation the unfiltrate flows via the fluid inlet 13 through the inlet filter 11 and the inlet side 9 into the inner cavity of the filter inserts 5 and 7, flows through the filter material to the outside and is discharged via the filtrate outlet 3. During the backflush operation, which takes place with an open backflush valve 33, the rotating drive shaft 23 moves the backflush arms 15 and 17. As a result, the backflush devices 21 with their slot-shaped flow passages 39, which are located at their free end face 37, are moved past the inside of the filter material 19 of the filter inserts 5, 7 without a gap. On the backflush devices 21, the slot-shaped flow passages 39 form the inlet of their internal flow chamber, which is connected to the tube-shaped drive shaft 23. With the backflush valve 33 open, the slot-shaped flow passages 39 are subjected to the pressure differential between the system pressure on the filtrate side that surrounds the filter inserts 5, 7 and the pressure in the drive shaft 23, which may, for example, correspond to the ambient pressure. At this pressure differential, which is in the vicinity of 1.5 bar at the usual system pressure, particles deposited at the slotted nozzle-shaped flow passages 39 are detached and pass through the inner flow chamber of the backflush devices 21 into the drive shaft 23 and from there via the discharge tube 31 to the outside. Instead of the ambient pressure it is possible to generate a negative pressure in the drive shaft 23 by means of a suction fan (not shown).

The FIGS. 2 and 3 depict the geometry of the inner flow chamber 41 of the backflush devices 21 provided in the exemplary embodiment of FIG. 1, wherein three backflush devices 21 each are attached to the backflush arms 15 and 17 vertically one above the other in such a way that their flow passages 39 adjoin each other and form a slot that extends over the entire height of the inside of the filter material 19.

The FIGS. 2 to 4 depict the geometry of the flow chambers 41 of the backflush devices 21 provided in the example of FIG. 1. As is apparent from FIG. 3, in which the horizontal cross-section of the flow chamber 41 is shown in the plane that extends vertical to the plane of the flow passage 39, the flow chamber 41 expands continuously from the inlet opening 39 towards the outlet 43 that is attached to the drive shaft 23, wherein the side walls 45 of the flow chamber 41 diverge planar to each other. The path taken by the upper and lower boundary wall is apparent from FIG. 2. As depicted, the upper boundary wall 47 takes a straight, inclined path starting from the upper end of the flow passage 39 in the direction of the lower boundary wall 49, which extends along a level path in the horizontal plane that extends perpendicular relative to the direction of the flow passage 39. The upper and lower boundary wall 47 and 49 enclose the angle designated with al in FIG. 2, which in the present example is 38°. At a transition designated with 51 in FIG. 2, which is located at a distance from outlet 43, the upper boundary wall 47 changes from an inclined path to a parallel path relative to the lower boundary wall 49, so that an outlet tube 52 is formed between the transition 51 and the outlet 43. In the example shown, the distance between the transition 51 and the outlet 43 is approximately equal to the diameter of the outlet tube 52. Said outlet tube 52 has, in the example shown, a diameter of 21 mm at a slot height of the flow passage 39 from 80 to 120 mm, and a slot width of 0.5 to 10 mm. The divergence of the side walls 45 is advantageously in the range from 4° to 8°. In the present example the angle is 5.3°. As shown in FIG. 4, the boundary walls 45 are provided with a fillet 54 at the entry point 53 of the slot-shaped flow passage 39. As depicted in FIG. 2, beginning at the flow passage 39, two wing-shaped flow guide vanes 55 and 56 are provided in the flow chamber 41, which extend between the side walls 45 towards the outlet 43. In this instance the flow guide vane 55, which is positioned out of center towards the top of the flow passage 39, extends over approximately one quarter of the length of the flow chamber 41, measured in radial direction, whereas the lower flow guide vane 56, which starts somewhat below the center of the height of the flow passage 39, is of a reduced length.

FIG. 5 depicts a further exemplary embodiment of the filter device according to the invention. This corresponds with the first exemplary embodiment, except that disposed on the drive shaft 23 for each filter insert 5 and 7 are two backflush devices 21, located one above the other, the flow chambers 57 of which have a different shape compared to the flow chambers 41 of the first example. The backflush devices 21 of the example in FIG. 5 and the geometry of their flow chambers 57 are shown in greater detail in FIGS. 8 to 11. As shown in FIGS. 8 and 9, the backflush devices 21 of this example come in form of a body with two flat lateral surfaces 58, which extend from both planes to the outlet 43 at the long sides 59 of the free end face 37, where said planes are parallel to the slot-shaped flow passage 39, wherein the width of the lateral surfaces 58 reduces towards the outlet 43 in two steps 60 and 61. Whilst in the first example the upper boundary wall 47 and the lower boundary wall 49 of the inlet funnel extend in a straight line from the flow passage to outlet 43, in the second example both boundary walls 47 and 49 extend along the same parabolic curve (see in particular FIG. 6). As indicated there, this path causes a widening of the inflow funnel that corresponds to an opening angle of α2, which in the current example is 63°. The ratio of slot height to slot width of the flow passage 39 is 61 in this exemplary embodiment. As in the first example, the side walls 45 diverge from the flow passage 39 to the outlet 43 at an angle that is 6° in the example shown. As in the first exemplary embodiment, the area ratio of the slot entry of the flow passage 39 and the channel exit at the outlet 43 is in the range between 0.2 and 2.0, and is in the present example 0.7. Also corresponding to the first exemplary embodiment, the ratio of the width of the slot-shaped flow passage 39 to the free diameter of the tube-shaped or channel-shaped section at outlet 43, that is, at the transition to the internal fluid conductance of drive shaft 23, is in the range from 0.05 to 0.5, and is in the depicted example 0.1.

A further difference compared to the first exemplary embodiment lies in the fact that three flow guide vanes 55, 56 are disposed inside the flow chamber 57. Of those, the first flow guide vane 56, which is situated centrally on the symmetrical axis between the boundary walls 47 and 49, is longer than the two further flow guide vanes 55, which are disposed in the area between the central flow guide vane 56 and the upper boundary wall 47 and in the area between the lower boundary wall 49 and the central flow guide vane 56. The shorter flow guide vanes 55, which both have the same shape and which extend with their concave curvature facing the adjacent boundary wall 47, 49, are arranged such that the flow chamber 57 takes on a symmetrical cross-sectional shape, wherein the tapered, inner ends 63 of the flow guide vanes 55 are at a lesser distance from the respective adjacent boundary wall 47 and 49 than the rounded noses 65, which in turn have the same distance from the rounded nose 65 of the central guide vane 56 at the flow passage 39 (see FIG. 6).

For the backflush devices 21 for the exemplary embodiment in FIG. 5 the FIGS. 13 and 14 show a flow chamber 67 with a slightly modified geometry. In contrast to the above-described example, the upper boundary wall 47 and the lower boundary wall 49 are not parabolic but extend in a straight line. In symmetrical adaptation to this, the shorter flow guides 55 are not curved but straight, although the positioning is the same as in the above-described example. The angle and area ratios also correspond to those of the above-described example.

The FIG. 15 depicts a further exemplary embodiment of the filter device according to the invention. Four backflush devices 21, one above the other, are provided for each filter insert 5 and 7, which essentially correspond to the backflush devices 21 of FIGS. 8 to 11, that is, they correspond to the flow chamber 57 with parabolic boundary walls 47, 49 and with three flow guide vanes 55, 56 depicted there. However, in the example of FIG. 15, said backflush devices 21 are part of a common retainer housing 69 which, as shown more clearly in FIG. 16, consists of an upper housing half 71 and a lower housing half 73, each of which forms the outlet 43 for two backflush devices 21. FIGS. 17 and 18 show a variation of this exemplary embodiment in which the retainer housing 69 takes the shape of a rail member 75 that may be attached to the outside of the drive shaft 23, which is preferably formed by a square tube, wherein the rail member 75 may be attached and in which insertion slots 77 are formed, into which the backflush devices 21 may be inserted in form of exchangeable inserts 78 (see FIG. 8), which depicts a backflush device 21 prior to insertion. The external shape of the backflush devices 21 as inserts 78 correspond, as shown in FIG. 18, essentially to the external shape of the backflush device 21 shown in FIGS. 8 to 11 apart from the fact that the narrow sides are stepped only once. Whilst in the example of FIGS. 17 and 18 the flow chambers have the same geometry as the flow chamber 57 (see FIG. 3), backflush devices 21 with differently-shaped flow chambers 41 or 67 may be installed as inserts 78 into the insertion slots 77 of the retainer housing 49.

Since in FIGS. 1, 5 and 15 only one backflush arm 15 and 17 respectively are provided each on the drive shaft 23 for each filter insert 5 and 7, different arrangements are possible. The FIGS. 19a to 19d depict examples of possible configurations. As shown in FIGS. 19a, 19b and 19d , for each filter insert 5 or 7 more than one backflush arm is provided, of which, in the example of FIG. 19a , each is provided with three backflush devices 21 in an arrangement adjacent to one another. FIG. 19b also shows two backflush arms for each filter insert 5, 7, wherein each backflush arm is provided with three backflush devices 21 that are arranged at a distance from each other, and wherein the backflush devices 21 of the one backflush arm are directed into the gaps between the backflush devices 21 of the other backflush arm. As shown in FIG. 19c , only one backflush arm is provided for each filter insert 5, 7, in which six backflush devices 21 are provided adjacent to one another. The FIG. 19d on the other hand shows for each filter insert 5, 7 two backflush arms, of which the one shown on the right hand side of the figure is provided with two backflush devices 21, which are located at a height of a gap between two upper backflush devices 21 and two lower backflush devices 21 of the other backflush arm. The FIGS. 20a to 20c depict examples of possible distributions of backflush arms 79 inside their turning circle 81.

Besides filtration of lubrication oil, the filter device according to the invention may also be used for other applications for which it is suitable. Apart from the already mentioned maritime application in which ballast water in ships is cleaned, the device may also be used to treat process water. 

1. A filter device comprising a filter housing (1) with a fluid inlet (13) for unfiltrate and a fluid outlet (3) for filtrate and with at least one single-part or multi-part filter insert (5, 7) accommodated inside the filter housing (1), wherein said filter insert (5, 7) may be cleaned through a reverse flow with at least one backflush device (21), which is moveable by means of a fluid-conducting drive shaft (23) of a rotary drive (35) on the inside of the filter material (19) of the respective filter insert (5, 7), and is provided with a slot-shaped flow passage (39) at its end that is adjacent to said inside of the filter material (19), wherein said slot-shaped flow passage (39) extends parallel to the rotational axis of the drive shaft (23) and which leads into a flow chamber (41; 57; 67) that has a fluid connection with the drive shaft (23), wherein said flow chamber (41; 57; 67) tapers at least partially in the direction of the drive shaft (23) in a first plane in which the flow passage (39) is located, characterized in that in a further second plane, which extends transverse to the first plane, the flow chamber (41; 57; 67) widens out, continually at least in part, starting from the flow passage (39) and in the direction of the drive shaft (23).
 2. The filter device according to claim 1, characterized in that in the first plane the flow chamber (41; 57; 67) is continuously tapered as a kind of inlet funnel.
 3. The filter device according to claim 1, characterized in that, starting from the slot-shaped flow passage (39), formed in the first plane are at least one boundary wall (47) of the inlet funnel extending obliquely and a further boundary wall (49) extending level; two boundary walls (47, 49) extending obliquely and in a straight line; two boundary walls (47; 49) extending parabolically; and one boundary wall obliquely and in a straight line, and the further boundary wall curved.
 4. The filter device according to claim 1, characterized in that, in the direction of the flow linkage of the flow chamber (41; 57; 67) to an internal fluid passage of the drive shaft (23), the respective flow chamber (41; 57; 67) merges with its boundary walls (45, 47, 49) into a tube-shaped or channel-shaped section (52) in which the boundary walls (45, 47, 49) extend in a straight line.
 5. The filter device according to claim 1, characterized in that in the second plane, the flow chamber (41; 57; 67) expands from the slot-shaped flow passage (39) in the direction of the internal fluid passage of the drive shaft (23) in a conical manner with straight boundary walls (45).
 6. The filter device according to claim 1, characterized in that the flow chamber (41; 57; 67), at its exit from the backflush device (21) in the direction of the respective filter insert (5, 7), is provided with at least one fillet (54) at the boundary walls (45) of the slot-shaped flow passage (39), which extends parallel to the rotational axis of the drive shaft (23).
 7. The filter device according to claim 1, characterized in that the area ratio between slot inlet and channel exit (43) is in the range from 0.2 to 2.0, preferably from 0.3 to 1.0.
 8. The filter device according to claim 1, characterized in that the expansion of the slot-shaped flow passage (39) of height to its width is preferably in the range from 10 to 100, preferably in the range from 30 to
 70. 9. The filter device according to claim 1, characterized in that the ratio of the width of the slot-shaped flow passage (39) to the free diameter of the tube-shaped or channel-shaped section (52) at the transition to the internal fluid passage of the drive shaft (23) is between 0.05 and 0.5.
 10. The filter device according to claim 1, characterized in that wing-like flow guide vanes (55, 56) are disposed inside the flow chamber (41; 57; 67), which extend at least in part from the slot-shaped flow passage (39) away in the direction of the channel exit (43).
 11. The filter device according to claim 1, characterized in that at least some of the flow guide vanes (55, 56) extend in a curved or straight manner, and extend fully between the boundary walls (45) of the backflush device (21), which extend parallel to the rotational axis of the drive shaft (23).
 12. The filter device according to claim 1, characterized in that at least one flow guide vane (55) protrudes, starting from the slot-shaped flow passage (39), further into the flow chamber (41; 57; 67) than at least one further flow guide vane (55), wherein the further protruding flow guide vane (56), which is preferably disposed in the center of the slot-shaped opening of the flow passage (39), extends from there in the direction of the inside of the flow chamber (41; 57; 67).
 13. The filter device according to claim 1, characterized in that the fluid passes inside the flow chamber (41; 57; 67) from the slot inlet without diversion of the overall flow of the backflush volume up to before the channel exit (43).
 14. The filter device according to claim 1, characterized in that the respective backflush device (21), which faces the internal wall of the filter material (19) of the respective filter insert (5, 7) with its one free end face (37), is moved past said internal wall without a gap by means of the rotatable drive shaft (23).
 15. The filter device according to claim 1, characterized in that inserted backflush devices (21) are exchangeably retained in an associated retainer housing (69), which is disposed on the drive shaft (23).
 16. The filter device according to claim 1, characterized in that multiple backflush devices (21) are inserted along the drive shaft (23), one above the other, wherein they are disposed in at least two groups combined at different circumferential positions on the drive shaft (23), preferably diametrically opposed to each other with respect to the rotational axis of said drive shaft; in one group, exclusively on one side of the drive shaft (23); or in alternating succession on opposite sides of the drive shaft (23). 